JPH06138542A - Device and method for reading bar code - Google Patents

Abstract

PURPOSE:To prevent a bar code from being erroneously read because of chattering by making the outputted signal from a bar code sensor pass through a frequency filter circuit first so that a high-frequency component such as chattering noise may be eliminated. CONSTITUTION:The bar code 15 passing through the front surface of the bar code sensor 7 at a constant speed is read by the bar code sensor 7 while a bar code board 14 rotates. The bar code sensor 7 outputs an OFF signal while detecting a black bar and outputs an ON signal while detecting a white bar to a bar code reader 31. As to the outputted signal; after high-frequency chattering noise component having a short cycle is eliminated, only low-frequency signal component having a long cycle pass through to be converted to a binarized signal at a frequency filter circuit 34 first, then a binary number is inputted to a shift register 33, and is outputted to a controller 40. Thus, data is read by the controller 40.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bar code reading apparatus and a reading method for a photographic film cartridge in which reading errors due to chattering are eliminated.

[0002]

2. Description of the Related Art Photographic films are classified according to their type,
A DX code is provided so that various kinds of information specified at the time of manufacturing, such as the film sensitivity, the number of images that can be taken, the expiration date, the manufacturing lot, and the manufacturer, can be easily known. The DX code includes a method of reading data written in the magnetic recording layer of the photographic film with a magnetic head and a method of reading a bar code written on a film cartridge with a bar code sensor. Recently, a disc-shaped bar code plate incorporated in a photo film cartridge is rotated in conjunction with the spool rotation shaft, and the bar code plate and bar code sensor are moved relative to each other to read out information unique to the photo film. A camera for identifying a photographic film cartridge and its bar code has been devised (eg, US Pat. No. 5,04,04).
9, 912).

When the DX code of the above-mentioned method is used, in order to read the information from a bar code described in high density for the purpose of including as much information as possible, the bar code plate is rotated at a constant angular velocity. If not, the control circuit must always be able to detect the rotation amount by an encoder that generates a pulse in synchronization with the unit rotation angle. However, the spool rotating shaft is originally intended to rotate for feeding the photographic film, and feeding at a constant angular velocity is not considered. That is, the film feed speed greatly changes depending on the temperature, the remaining battery level, the frame position of the photo film, etc., and the angular velocity of the spool rotating shaft also greatly changes accordingly. Therefore,
It has been proposed to read the barcode immediately after loading the photographic film, which is not affected by the shooting conditions. In this case, it is conceivable to read the bar code at the initial feeding of the photo film or when setting the first shooting screen,
In either case, the spool rotation shaft rotates at a substantially constant angular velocity.

[0004]

However, since the spool rotary shaft is rotated by a motor such as a DC motor or a coreless motor or a gear train and is affected by friction, it actually rotates at a constant angular velocity. Things are rare. Further, since the spool rotating shaft makes unstable rotation, a slight vibration also occurs in the bar code plate fixed to the spool rotating shaft, which often causes chattering in the detection signal of the bar code sensor to cause a reading error. is there.

The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide a bar code reading apparatus and a reading method for a photographic film patrone that avoids reading errors due to chattering.

[0006]

In order to achieve the above object, the present invention provides an original signal from a bar code plate which is rotatably housed in a photographic film cartridge and rotates in association with a spool around which the photographic film is wound. A sensor for reading
A bar code reader is composed of an amplifier having a filter circuit for cutting a high frequency signal contained in an original signal from the sensor and a binarizing circuit for binarizing the signal from the amplifier. .

According to a second aspect of the present invention, there is provided a bar code reading method in which a first timer measures a fixed time in response to a change in the level of the binarized signal, and the level change of the binarized signal is detected during the time period. In addition to ignoring, the second timer measures time in synchronization with the start or end of time measurement of the first timer, and after the time measurement of the first timer ends, a level change of the binarized signal is made during the time measurement period of the second timer. The time width data of the binarized signal is detected during the period from the start of the time measurement of the first timer to the end of the time measurement of the second timer when the time measurement of the second timer is completed.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 shows an example of a camera embodying the present invention. A shutter button 3, a finder window 4, and an exposure mode changeover switch 5 are provided on the surface of the camera body 2. Further, a cartridge storage chamber 6 is provided inside the main body 2, and a bar code sensor 7 is provided at the bottom thereof.
Are arranged. When the upper lid opening / closing lever 8 is slid, the upper lid 9 formed on the upper surface of the main body 2 is opened, and the photographic film cartridge 10 is loaded in the cartridge storage chamber 6.

FIG. 1 schematically shows a bar code reading apparatus of the present invention. Photo Film Patrone 10
A spool rotation shaft 11 is rotatably attached to the spool rotation shaft 11, and the spool rotation shaft 11 is rotated by a motor 12. One end of a photographic film 13 is fixed and wound around the spool rotating shaft 11. A bar code plate 14 is fixed to the upper portion of the spool rotation shaft 11, and a bar code 15 is recorded on the bar code plate 14 in the circumferential direction. A window 16 for exposing the barcode 15 of the barcode plate 14 to the outside is formed on the upper portion of the photographic film cartridge 10, and when the photographic film cartridge 10 is loaded in the cartridge storage chamber 6, the barcode 15 and the barcode are The sensor 7 faces the window 16.

As shown in FIG. 3, the bar code 15 is composed of a black bar 20 and a white bar 21 having various widths, and various unit bars represent various information. Further, at the start position of the bar code 15, a start code 22 composed of a black bar 20 wider than any other bar is written. Bar code sensor 7
A reflection type photo sensor is used for this, and when the black bar 20 of the bar code 15 is detected, "OF
The “F” signal is output as “O” when the white bar 21 is detected.
The N ”signal is output to the barcode reading device 31.

The bar code reading device 31 includes an amplifier 3
2 and a shift register 33, and an amplifier 32
Is composed of a frequency filter circuit 34, an amplifier circuit 35, and a binarization circuit 36. In addition, the frequency filter circuit 34
Is a high cut filter circuit 34a, as shown in FIG.
And a low-cut filter circuit 34b, as shown in FIG.
The high frequency band F _h and the low frequency band F _l having the frequency characteristics shown in are cut, and only the signal in the middle frequency band F _m is passed.

The original signal obtained from the bar code sensor 7 is amplified by the amplifier circuit 35 after the high frequency component is removed by the frequency filter circuit 34, and output to the binarization circuit 36. The binarization circuit 36 converts the input signal into a binarized signal, and then inputs a binary number corresponding to the holding time of each of the “ON” and “OFF” states of the binarized signal to the shift register 33. The shift register 33 repeatedly inputs the binary numbers of the bars forming the barcode 15 one by one, and when the input of the binary numbers of all the bars is completed, outputs a series of data to the controller 40. The data thus output from the barcode reading device 31 is decoded by the controller 40.

The operation of the above configuration will be described. When the photographic film cartridge 10 is loaded into the cartridge storage chamber 6 and the upper lid 9 is closed, the motor 12 is driven and the automatic film feeding is started. As is well known, in this automatic film feeding, the front end of the photographic film 13 is wound around the winding shaft of the camera, and the first frame is set in the exposure frame of the camera. During the transfer of the photographic film 13, the spool rotary shaft 11 rotates, and the bar code plate 14 fixed to the spool rotary shaft 11 also rotates at a constant angular velocity. At the same time, the barcode sensor 7 and the barcode reading device 31 are activated.
Then, while the bar code plate 14 is rotating, the bar code sensor 7 reads the bar code 15 passing through the front surface thereof at a constant speed. The bar code sensor 7 sends an “OFF” signal while the black bar 20 is being detected, and the white bar 2
While detecting 1, the “ON” signal is output to the barcode reading device 31.

The output signal of the bar code sensor 7 includes an "ON" signal and an "OF" signal having a duration of a certain time or more.
It contains a signal component of the "F" signal and a chattering noise component having a very short duration due to an instantaneous signal change. Considering the duration of these signals as a half cycle of a sine wave, the chattering noise component in which the signals last only momentarily has a very short cycle. Therefore, in the output signal of the barcode sensor 7 sent to the barcode reading device 31, first, the frequency filter circuit 34 removes the chattering noise component of high frequency having a short cycle, and passes only the signal component of low frequency having a long cycle. To be done.

The signal component passing through the frequency filter circuit 34 is amplified by the amplifier circuit 35 and then sent to the binarization circuit 36. As described above, the bar code plate 14 rotates at a substantially constant angular velocity, and since this rotation angle is proportional to time, the detection time of each bar can be directly associated with the bar width. Therefore, the signal component sent to the binarization circuit 36 corresponds to each holding time of the “ON” signal and the “OFF” signal indicating the detection time of each bar after being converted into the binarized signal here. The binary number is input to the shift register 33.

Each time the bar code sensor 7 passes through the bar forming the bar code 15, the shift register 33 is repeatedly input with one binary number corresponding to the bar width. The input of the binary number is repeated until the binary number corresponding to the start code 22 is input to the shift register 33 twice. Then, when the binary number of the start code 22 is input the second time, the input of the binary numbers of all the bars is completed, and the shift register 33 receives the binary number of the start code 22 input the first time and the second time. A series of data stored between the start code 22 and the binary number input to is output to the controller 40. The data thus output from the barcode reading device 31 is decoded by the controller 40.

In the above embodiment, the bar code is read when the film is automatically fed immediately after the photographic film is loaded. However, it is interlocked with the frame feeding of the photographic film each time the power switch of the camera is turned on. The barcode may be read at any time.

Next, a second embodiment of the present invention will be described with reference to FIG. The same members as those in the embodiment shown in FIG. 1 are designated by the same reference numerals. In this embodiment, attention is paid to a time zone in which chattering noise may occur, and a signal change in this time zone is invalidated.
The barcode reading device 50 includes an amplification circuit 35, a binarization circuit 36, a barcode detection time calculation unit 51, and a shift register 33. Further, the barcode detection time calculation unit 51 counts the time for rejecting the signal from the barcode sensor, and the second timer 52 for measuring the time during which the barcode sensor 7 detects each bar.
The timer 53 and a calculation unit 54 that calculates the detection time of each bar from the specified time of the first timer 52 and the measurement time of the second timer 53.

FIG. 7 shows a change in each signal of the bar code detection time calculation section 51. The bar code sensor signal (a) represents the detection status of the bar code sensor 7, and is “OFF” while the black bar 20 in FIG. 3 is being detected.
Is displayed, and “ON” is displayed while the white bar 21 is being detected. The first timer signal (b) counts "D" for a certain period of time after the bar code sensor signal (a) has changed, and the change in the bar code sensor signal (a) at this time is detected by the signal. Edge detection at switching is performed. The second timer signal (c) measures the time from when the first timer signal (b) finishes counting "D" for a certain time to when the barcode sensor signal (a) changes next.

On the other hand, the chattering noise is instantaneously generated immediately after the signal switching, and the time zone in which the chattering noise may occur is shorter than the time when one thinnest bar is detected. Therefore, the fixed time “D” counted by the first timer signal (b) is set to be shorter than the detection time of one bar, including the time period in which the chattering noise may occur, completely. If so, it can be determined that the signal change occurring within this time is due to chattering noise, and the change in the barcode sensor signal (a) can be ignored. Therefore,
The detection time of each bar can be calculated by adding the fixed time “D” of the first timer signal (b) to the measured value of the second timer signal (c), and the calculation unit 54 performs this processing. .

Next, according to the flow chart of FIG.
The operation of the embodiment will be described. When the motor 12 is driven and the automatic film feeding is started, the bar code plate 14 starts to rotate at a constant angular velocity, and at the same time, the bar code sensor 7 and the bar code reading device 50 operate. The bar code sensor 7 outputs an “OFF” signal while detecting the black bar 20 and outputs an “ON” signal while detecting the white bar 21. The original signal of the barcode sensor 7 is the amplification circuit 3
After being amplified at 5, it is converted into a binarized signal by the binarizing circuit 36 and output to the barcode reading device 50.

In the bar code reading device 50, the start code 22 is read, and when the output signal from the bar code sensor 7 changes from "OFF" to "ON", the first timer 52 starts counting, and this count value Even if a change in the signal due to chattering noise occurs before changes to “D”, this change is invalidated.

When the count value of the first timer 52 reaches "D", the first timer 52 stops counting and the change in the signal from the bar code sensor 7 becomes effective from this point.
At the same time, the second timer 53 operates to measure the holding time until the signal from the barcode sensor 7 changes again. The signal from the barcode sensor 7 changes from "ON" to "OFF"
When the value changes to, the second timer 53 stops the measurement, and at the same time, the first timer 52 starts counting, and at this time point, the change in the signal from the barcode sensor 7 is ignored again.

The value measured by the second timer 53 is
After it is confirmed that the time required to detect the widest start code 22 is shorter than “C”, the operation unit 5
4 is output. At this time, if the measured value of the second timer 53 is equal to or longer than the time “C”, this value is the detection time of the start code 22, so the bar code plate 14 makes one rotation to complete the detection of all the bars. It will be. Therefore, the bar code reader 50 stops at this point.

The calculation unit 54 adds the fixed time "D" of the first timer 52 to the measured value of the second timer 53 to calculate the detection time of the first white bar 21. Then, a binary number corresponding to the calculated bar detection time is input to the shift register 33.

When the shift register 33 completes the input of the detection times of all the bars by repeating the above processing, it outputs a series of data to the controller 40. The data thus output from the barcode reading device 50 is decoded by the controller 40.

[0027]

As described above, according to the present invention, since the output signal of the bar code sensor first passes through the frequency filter circuit, high frequency components such as chattering noise are removed. In addition, focusing on the time zone in which only chattering noise may occur, and changing the signal during this time zone is invalidated, it is possible to prevent bar code reading errors due to chattering and to avoid malfunctions. it can.

[Brief description of drawings]

FIG. 1 is a schematic view showing a first embodiment of a bar code reading apparatus of the present invention.

FIG. 2 is a perspective view showing an example of a camera including the barcode reading device of FIG.

FIG. 3 is a partial plan view showing a barcode plate.

FIG. 4 is a circuit diagram showing a frequency filter circuit in the barcode reading apparatus of FIG.

5 is a graph showing frequency characteristics of the frequency filter circuit of FIG.

FIG. 6 is a schematic view showing a second embodiment of the barcode reading device of the present invention.

7 is a timing chart showing each signal of a barcode detection time calculation unit in the barcode reading apparatus of FIG.

FIG. 8 is a flowchart showing a barcode detection time calculation sequence.

[Explanation of symbols] 7 bar code sensor 10 photo film cartridge 11 spool rotating shaft 13 photo film 14 bar code plate 31,50 bar code reader 32 amplifier 34 frequency filter circuit 36 binarization circuit 40 controller 51 bar code detection time calculation Unit 52 first timer 53 second timer 54 computing unit

Claims (2)

[Claims] 1. A sensor, which is rotatably housed in a photographic film cartridge and reads an original signal from a bar code plate which rotates in association with a spool around which the photographic film is wound,
A bar code reader comprising an amplifier having a filter circuit for cutting a high frequency signal included in an original signal from the sensor, and a binarizing circuit for binarizing the signal from the amplifier. . 2. A bar code reading device which is rotatably housed in a photo film cartridge and which reads a binarized signal from a bar code plate which rotates in conjunction with a spool around which the photo film is wound to obtain information specific to the photo film. In the method, in response to a change in the level of the binarized signal, a first timer measures a certain period of time, ignores the change in the level of the binarized signal during this time period, and starts or measures the time of the first timer. The second timer counts in synchronization with the end, and when the level change of the binarized signal is detected during the counting period of the second timer after the counting of the first timer ends, the counting of the second timer ends, A bar code reading method, wherein time width data of a binarized signal is detected depending on a period from the start of timing of the first timer to the end of timing of the second timer.